Recently, inexpensive and pervasive networking technologies based on various small devices are emerging or being commercialized. People can make good use of various home appliances such as refrigerators, TVs, washing machines, PCs, and audio equipments once such appliances are connected to a home network. For the purpose of such home networking, UPnP™ (hereinafter, it is referred to as UPnP for short) specifications have been proposed. UPnP technology employs distributed and open network architecture, enabling the user to control respective devices of various types or services provided by the devices by using one or more than one control point (in general, it is termed as ‘CP’ for short) based on well-known standard networking technologies such as IP (Internet Protocol), HTTP, and so on.
UPnP technology automatically discovers a UPnP compliant device (and a service provided by the device) on a network, models the service of the corresponding device as state variables, and enables a control point or another device to use the modeled service. A control point (CP) is one of control applications and a plurality of CPs can be installed together in a particular UPnP device carrying out a different service. Also, CPs can be installed individually distributed over a number of devices.
Meanwhile, an AV home network based on UPnP can be equipped with a device carrying out the role of a server such as an AV media server or PM (Power Management) server; and a device carrying out the role of a media renderer such as a digital television.
An AV media server is a device providing various media files to be reproduced through a media renderer; a PM server carries out power management (management of a state such as active, sleep, and hibernation) about physical resources where the server is installed.
In this way, a PM server can be realized as a single independent device or can be realized together in a device of another function. The latter case is called as an embedded device; for example, an AV media server and PM server can be implemented in a single device.
An AV media server (or a device providing a different service) and PM server are controlled independently by separate control points. Generally, a control point which controls the former is called as an AV control point; while a control point which controls the latter is called as a PM control point. Since a PM CP discovers PM servers only and carries out controlling thereof, unless the user recognizes implementation forms of all the devices on a network, the user will not be able to figure out which PM server should be controlled through the PM CP in order to control power status of an associated device or resources of the device. For example, when an embedded device exists on a network, where an AV media server and PM server are implemented together, even if the user wants to check or change the power status of an AV media server of the embedded device, it cannot be known with a list of discovered PM servers which PM server carries out the role.